The present invention is directed, in general, to a method of coil preparation for an ionized metal plasma process.
In the field of semiconductor device fabrication, the continuing trend toward smaller device feature sizes continues to challenge current process technologies. One such process that is currently employed to aid in achieving these small device dimensions is an ionized metal plasma (IMP) deposition process. Such IMP processes may be used to sputter deposit films of metal or metal-containing compounds and leads to better bottom and sidewall step coverage from the directionality afforded by the target/coil configuration in an IMP process for a variety of device structures. These advantages allow the use of relatively thinner films in forming the device features thereby saving on equipment and consumables and also significantly reducing the processing times for subsequent fabrication steps.
Current IMP processes typically employ deposition chambers that have a coil that aids in the ionization of atoms as they are sputtered from the target. Commonly the coil is composed of the same material as the target. For example, for depositing a titanium or titanium-containing film on a wafer, the titanium is used as the coil material. When another film composition is desired, the coil is composed of the corresponding metal.
During IMP deposition processes, the metal sputtered from the target builds up on the coil. It was discovered that this build-up of metal was a source of wafer contamination in that the built-up metal would often flake off of the coil and onto the wafer, thereby contaminating that particular level of the wafer. To reduce this contamination problem, the industry adopted a process of knurling the surface of the coil to increase adhesion of any metal deposited on the coil. Prior to use in conventional processing of semiconductor wafers, IMP coils are subjected to an extensive conditioning process, known as burn-in. During this conventional conditioning process, substantial quantities of material are deposited on the coil and on the walls of the deposition chamber. It had been thought that knurling of the coil surface provided sufficient adhesion between the deposited material and the coil surface.
However, this knurling process has proven unsatisfactory in the manufacture of semiconductor devices because it has been found that these conventional methods do not prevent delamination or flaking of the deposited metal to a satisfactory degree, even where a coil having a knurled surface is used. This delamination or flaking is thought to be caused by non-uniformities, such as voids, that form at the interface of the coil and the deposited metal, which are illustrated in FIGS. 1A and 1B. FIG. 1A is a cut away view of a section of the coil after deposition of a metal thereon. As seen in FIG. 1B, which is an enlarged view of FIG. 1A, voids have formed at the interface of the coil and the deposited metal. It is believed that these voids cause deposited metal to adhere poorly to the coil, which in turn, causes the deposited metal to flake off prematurely and thus shorten the useful life of the coil. For example, while the useful life of a coil is rated at approximately 400 kWh by the manufacturer, delamination may be observed after the chamber has been operated only about 150 kWh. Even when operated for less than 150 kWh coils may show bubbles or blisters, indicating that the delamination process has begun. It is thought that these blisters result from poor adhesion between the coil surface and the layers deposited during the conditioning process. The poor adhesion eventually leads to blister formation and their subsequent delamination. In severe cases, the delamination may cause a particle concentration that uses shorts or arcing in the fabricated devices, thereby reducing the wafer yield. When the wafer yield is so affected, the chamber must be taken off-line, cleaned, and the coil replaced. Lowered wafer yield and unit down time ultimately reduce revenue and increase product cost.
Accordingly, what is needed in the art is a process that improves adhesion and reduces delamination of the metal surface of the coil during operation.
To address the above-discussed deficiencies of the prior art, the present invention provides a method of depositing a film on a surface of a component of a deposition tool. In an advantageous embodiment, the method includes depositing a metal from a target onto a component""s surface of a deposition tool to form a first film on the component""s surface and forming a second film over the first film at a low pressure and at a first power at the target that is substantially higher than a first power at the component""s surface. In an exemplary embodiment the deposition tool may be a coil. It should, of course, be understood that the above process can be used for a processes for manufacturing integrated circuits.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.